* Caterpillar weighs on Dow after reducing 2013 forecast
* Facebook's best daily percentage gain ever keeps Nasdaq aloft
* Investors worry about China's growth after Chinese stocks slide
* U.S. jobless claims rise modestly in latest week
* Dow down 0.4 pct; S&P 500 off 0.2 pct; Nasdaq up 0.2 pct
By Ryan Vlastelica
NEW YORK, July 25 (Reuters) - U.S. stocks mostly slipped on Thursday, with cyclical sectors falling on some disappointing earnings and concerns about China's growth, though Facebook's rally gave the Nasdaq a lift.
The S&P 500 was on track for a third straight day of losses, while the Dow was set for a second negative day after Caterpillar Inc cut its 2013 earnings forecast. Caterpillar's stock slid 2.1 percent to $81.65 and ranked as the Dow's second-biggest percentage decliner.
The stock of Facebook Inc scored its biggest daily percentage gain ever - up 28.3 percent to a session high of $34. At midday, Facebook's stock was up almost 26 percent at $33.37 and topped the Nasdaq's list of most actively traded stocks a day after the online social network company posted a steep jump in mobile advertising revenue.
General Motors and Dow Chemical reported profits that topped expectations, but that was not enough to give the broad stock market a push into positive territory. GM's stock fell 1.5 percent to $36.59, after earlier touching a two-hear high at $37.70. Dow Chemical's shares, in contrast, gained 1.3 percent to $34.83.
Stocks have climbed steadily this year, with the S&P 500 gaining 18 percent in 2013, hitting a number of record closing highs. The index has advanced 4.7 percent in July so far.
"It's positive that markets are holding in relatively well, given how strong the month has been," said Mitch Rubin, chief investment officer of RiverPark Advisors in New York. "To the extent that earnings continue to be strong, that helps to take off some of the perception that we've gone too far, too fast."
With 47 percent of the S&P 500 companies having reported earnings so far, about 68 percent have topped profit forecasts, above the historical average of 63 percent. About 56 percent have reported better-than-expected revenue, a rate that is under the historical average.
The Dow Jones industrial average was down 60.43 points, or 0.39 percent, at 15,481.81. The Standard & Poor's 500 Index was down 3.57 points, or 0.21 percent, at 1,682.37. The Nasdaq Composite Index was up 6.83 points, or 0.19 percent, at 3,586.43.
Growing worries about slowing growth in China also made U.S. investors nervous. A major index of Chinese stocks suffered its second straight loss on Thursday despite measures from China's government to spur the economy, including help for exports and railway investment. Data on Wednesday showed manufacturing in China running at an 11-month low in July.
"Companies that are centered around macro issues like China are proving to be controversial bets right now, given all the fears out there," said Rubin, who helps oversee $2.1 billion.
Shares of manufacturer 3M Co, a Dow component, fell 0.5 percent to $115.72 after the company's results.
The tech sector, particularly online companies, provided a bright spot in Thursday's session and helped the Nasdaq achieve a slim gain.
TripAdvisor Inc shares shot up 13.5 percent to $69.41 a day after reporting a jump in quarterly profit and revenue from its travel website. The stock helped bolster the Nasdaq and ranked as one of the S&P 500's best performers at midday.
Weekly jobless claims rose slightly, moving to 343,000 from 334,000 in the previous week. Analysts were looking for a read of 340,000.
New orders for durable goods rose 4.2 percent in June, far stronger than the 1.3 percent growth rate that had been forecast. Markets had little reaction to the data.
In Europe, shares fell as a raft of mixed results from blue chips and lingering concerns about the pace of growth in China triggered a bout of profit taking following recent sharp gains.